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Abstract

Processes for making microparticles, preferably containing an active agent, are provided. In a preferred embodiment, the process involves preparing (1) a dispersed phase containing an agent in a solution of polymer and a first solvent; (2) a continuous phase containing a surfactant, a second solvent that is totally or partially immiscible with the first solvent, and sufficient first solvent to saturate the continuous phase; and (3) an extraction phase that is a nonsolvent for the polymer, a solvent for the continuous phase components, and a solvent for the first solvent, wherein the continuous phase solvent has solubility in the extraction phase of between about 0.1% and 25% by weight. Then, the dispersed phase and the continuous phase are mixed to form an emulsion, and the emulsion is then briefly mixed with a suitable quantity of extraction phase to induce skin formation at the interface of the dispersed and continuous phases. Remaining solvent is removed by an evaporation process step. The emulsification and solvent removal steps are preferably conducted in a continuous process. The brief extraction step prior to evaporation minimizes the loss of active agent from the microparticles, and reduces the required volume of extraction phase as compared to other extraction-based processes. Alternate emulsification methods, such as nonstatic mixers or emulsion lag tube, and solvent removal methods, such as incremental extraction, cryogenic extraction, or membrane separation, also are provided, and can be used in various combinations to make microparticles.

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